Height of football

  • #1
138
0

Homework Statement



A quarterback throws a football with an initial speed of 19.0 m/s at an angle 30.5deg above the horizontal. Unfortunately, the pass is incomplete and the football drops to the ground, 35.0 m away from the quaterback. From what height was the football released? (no diagram provided)

Homework Equations



Vy= Vknoty - gt from which we get ttot= [tex]\frac{2Vosin\vartheta}{g}[/tex]
from the equation y= Voyty2-0.5gt0.52 we get hmax= v02sin2g[tex]\vartheta[/tex]/2g

The Attempt at a Solution


so to figure out far it goes i used the equation xmax= v0xttot where it wld now equal vknotcos[tex]\vartheta[/tex](2*vknot sin[tex]\vartheta[/tex]/g) + distance it travelled and i wanted to know what i was doing wrong thanx :))
 

Answers and Replies

  • #2
Cyosis
Homework Helper
1,495
0
Not sure what you're doing here. You set v_y=0 when the ball touches the ground? This is not true for if there had been no ground it would have continued to fall.

You know the ball traveled a distance of 35 meters in the x-direction. So you can calculate how long it took for the ball to reach that position with [itex]x=v_x t[/itex]. Knowing the flight time you can solve the initial height by using [itex]y=y_0+v_0 t-1/2 gt^2[/itex].
 
  • #3
138
0
why wld the velocity be v0 and not Vy??
 
  • #4
Cyosis
Homework Helper
1,495
0
It's not I just listed the general kinematic expression for a falling object. In your case the vertical starting velocity is v_y.
 
Last edited:
  • #5
138
0
thanx :))
 

Related Threads on Height of football

Replies
5
Views
3K
Replies
3
Views
713
  • Last Post
Replies
1
Views
20K
Replies
1
Views
2K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
14
Views
2K
  • Last Post
Replies
6
Views
3K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
5
Views
5K
  • Last Post
Replies
3
Views
2K
Top